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The 8.2-magnitude earthquake that rumbled off the northern coast
of Chile on Tuesday (April 1) was located along the Pacific Ring
of Fire, where plate boundaries grind past each other, producing
tremors all the time.

But this particular quake struck smack in the middle of a
320-mile (500 kilometers) stretch of Chile's coast that had been
alarmingly quiet for more than a century, said Rick Allmendinger,
a geologist at Cornell University. [ The
10 Biggest Earthquakes in History ]

"The last earthquake in this segment was in 1877," Allmendinger
told Live Science. That 19th-century temblor, estimated to have
been 8.5 in magnitude, triggered a tsunami nearly 80 feet (24 m)
high and caused fatalities as far away as Hawaii and Japan.

Tuesday's event was much less devastating. There were six
reported deaths, a tsunami that rose to 8 feet (2.5 meters), and
some landslides, power failures and property
damage, according to the
Associated Press.

Despite the decades' worth of built-up stress that was released
in Tuesday's earthquake, there could be more energy stored along
the plate boundary, ready to unleash aftershocks or even a bigger
quake, Allmendinger said. It's possible that this tremor was a
"foreshock," like the strong rumblings that led up to the
9.5-magnitude quake that ripped along the coast of southern Chile
on May 22, 1960 — the
biggest earthquake on record.

"The longer you go without earthquakes,
the more likely it is that it will occur in the future,"
Allmendinger said. "That was the case in this particular
segment."

Earthquakes greater than 8 in magnitude don't occur every year.
Georgia Institute of Technology earthquake
researcher Andrew Newman said they happen, on average, every
2.5 years.

The first signs of trouble started a few weeks ago, Allmendinger
said. A magnitude-6.7 earthquake struck in the region on March
16, and it was followed by more than 60 earthquakes greater than
magnitude 4, and 26 earthquakes greater than magnitude 5,
according to the U.S. Geological Survey. But then the spot was
quiet for about week before the 8.2-magnitude quake hit on
Tuesday, about 59 miles (95 km) northwest of the port city of
Iquique.

Other researchers, too, are poring over data from Tuesday's
event, looking for connections that could help them explain or
predict the probability of big earthquakes. Newman, for example,
said the tremor might demonstrate how interconnected earthquakes
are in this region.

Tuesday's
Iquique earthquake occurred about 13 years after a
8.4-magnitude earthquake struck immediately north of it, off the
coast of southern Peru, Newman said. This pattern mirrors the
1877 Iquique earthquake, which occurred nine years after the
1868 Arica earthquake off the coast of southern Peru,
thought to have been at least 8.5 in magnitude, Newman said.

In other words, one big earthquake could increase the pressure in
another part of the plate boundary, triggering another big
earthquake years later.